And the British government was furious.
Back in the 1960s, when pop and rock were taking over the music scene, British teenagers had to turn to pirate radio stations to hear bands like the Beatles and the Rolling Stones.
Barred from broadcasting from land, stations such as Radio Caroline and Radio London had taken to the water, using rusty old ships moored in international waters to broadcast to millions of eager listeners across the UK.
The government wasn't happy and 50 years ago, on August 14 1967, the Marine Offences Act made it illegal to support the ships or broadcast from them.
The story of drama and intrigue and tragedy on the high seas inspired the movie The Boat that Rocked starring Bill Nighy.
The DJs — and their fans who remember that dark time — are marking the anniversary this weekend.
Australian DJ Ian Damon, who presented music for Radio London from onboard the ships, said he remembered the day the rebels gave up in defeat.
"When that transmitter finished with the playing of Paul Kaye saying 'And now Radio London is closing', we all had a tear as you can imagine," he said.
He is one of the original DJs taking part in commemorations in Essex where the last remaining ship, the MV Ross Revenge, sits just a few kilometres offshore.
The team from Radio Caroline still broadcast once a month and the original studio remains intact with a library of tens of thousands of records.
Original fans now at the helm
Manager Peter Moore said he always vowed to help Radio Caroline when he was old enough.
"The government were determined to suppress something that was enjoyable and completely harmless, and for me, and I was a young man at the time, that seemed so completely unfair and undemocratic," he said while onboard this week.
"I made myself a stupid promise that if I could ever help Radio Caroline I would, and here I am.
"Silliest thing I decided in my bloody life but here we are," he added with a laugh.
The ship attracts a slightly younger generation — men who grew up on Radio Caroline and have retired and have the time to present music shows.
"The ship was invisible over the horizon," Mr Moore said.
"It was this mysterious place from where music came and now that you can actually come and stand onboard it produces some very strong emotions."
Steve Anthony said he was inspired by Radio Caroline as a teenager but he had to wait until he had finished a career lasting more than 40 years before he had the time to join the station.
Station kept afloat by passionate presenters
Radio Caroline was the first pirate station and rivals soon followed, some operating from ships and others from old military forts in the Thames estuary.
"When the law was passed and the big stations shut down on August 14 1967, to us, I was a 16-year-old, I would say today it was the equivalent of taking away Facebook, Twitter, all the social media," he said.
"It was that important to us. It linked us all. It was the fabric of our lives.
"It sounds dramatic now and it only lasted three years but it was an intense three years," he said
Many of the DJs took risks to work on the ships.
They faced jail time and a lot of them could not swim.
Some of them had never been to sea.
"I used to read the news with a brown paper bag near me," Ray Clark said.
The pirate radio stations quickly attracted millions of listeners desperate to hear the Beatles and the Rolling Stones.
"After a couple of weeks we had more people listening than all of the BBC networks combined and that got up their nose somewhat because they were convinced there was no demand for this kind of music," Mr Moore said.
Mr Damon was nicknamed the Wombat and his call sign was "Hi there, you there".
He recalls singers like Lulu and Dusty Springfield coming out to the boats to promote their music.
"We were pioneers in broadcasting," he said.
Radio Caroline presenter Ray Clark remembers listening to Mr Damon as a nine-year-old on the radio.
"I think it lit a spark," he said.
"It was just so special and so different and worth fighting for."
Radio London shut down when the laws were brought in 1967 but Radio Caroline continued, although eventually ran out of steam.
A group of enthusiasts keep it operating on the Ross Revenge as well as onshore, and it has just been awarded its first AM radio licence.